The invention is intended for use in multiple microphone systems such as utilized in conference rooms. Specifically, the invention is directed toward "turning on" a microphone or allowing the sound received from the microphone to pass to the system output, such as a loudspeaker, only when the user of that microphone is talking. Ambient noise and sounds from others in the room do not turn on the microphone. Still more specifically, the method and apparatus which is utilized to achieve the end result, is one in which the time it takes for sound to travel a predetermined distance within the microphone is used to determine the direction from which the sound came. If the measured time is not within a prescribed period, then it means that the sound is coming from a direction other than the location of a desired or acceptable source and therefore the microphone is turned off, i.e., the sound is blocked from appearing at the output of the sound system.